A light-emitting diode (LED) has the advantages of small in volume, low power consumption, fast response time, providing colorful lights, and environment-friendly. Therefore, the LED has already become an important light emitting element in people's daily life. For example, the LED can be used as a light emitting element for a spot lamp to form an LED spot lamp.
The LED spot lamp is usually mounted to a fixed position for projecting light on a displayed object. However, the distance between the displayed object and the LED spot lamp is not always fixed while the conventional LED spot lamp has a fixed focal length. In the past, the conventional LED spot lamp is not adjustable in its focal length for emitting light. Thus, it is impossible to adjust the light focusing and light diffusing effects of the LED spot lamp when the same is used to illuminate the displayed object. In brief, the conventional LED spot lamp is inconvenient for use and would therefore result in poor illuminating effect.